1. Field of the Invention
The present invention relates to apparatus for guiding web material along a predetermined path and, more particularly, to an improved film guide for a film processor.
2. Description of the Prior Art
Numerous kinds of apparatus for processing photographic film have heretofore been devised. One well known apparatus which is adapted for use with film strip material, includes a plurality of tanks each of which contain a different film processing liquid such as developing solution, a fixing solution and a washing solution. The tanks are arranged in fixed, aligned relation in order that an exposed film strip may be advanced from tank to tank and successively treated by the different processing liquids. To effect such film strip advance the film processing apparatus further includes several groupings of vertically disposed rollers which are respectively immersed in the different processing liquids, within the tanks, for moving the exposed film strip through such liquids. Other rollers are located between the tanks for moving the exposed film strip from tank to tank. Together these rollers define a film strip advance path which interconnects the tanks. Upon rotatably driving all of the rollers, the exposed film strip will be moved along the film strip advance path from tank to tank and will be successively immersed in the different processing liquids. Such apparatus is disclosed in U.S. Pat. Nos. 3,779,439, 2,913,974, 1,574,591.
With each tank a plurality of rollers are rotatably supported on a rack. A first group of rollers cooperate to move the film strip in a downward direction generally within a vertical plane and a second group of rollers cooperate to move the film strip in an upward direction generally within a vertical plane which is spaced from and parallel to the first mentioned vertical plane. At the bottom of the tank a turnaround roller is positioned adjacent the lowermost roller of each group. The lowermost roller of each group is biased into contact with the turn around roller so that the film strip will move between the lowermost roller of the first group and the turn around roller, around the turn around roller and between the turn around roller and the lowermost roller of the second group and then upwardly through the other rollers of the second group. The film strip is typically guided around the turn around roller by guide shoes supported on the rack. One guide shoe positioned directly below the turnaround roller and between the two lowermost rollers provides a curved surface in close proximity to the turn around roller to cause the film strip to move in a curved semicircular path around the turn around roller to reverse its direction of movement from a downward direction to an upward direction.
While such prior art guide shoes serve their intended purpose they have certain disadvantages resulting from their rigid mounts and fixed position relative to the lowermost roller of each group and the turn around roller. Due to imperfect manufacturing processes the tolerance buildup between the rollers, the roller mounts, the rack interface for the roller mounts, the rack interface for the guide shoe mounts, the guide surface can add up to substantial dimensional variations. Also, because the lowermost rollers are biased into contact with the turn around roller passage of the film between each lowermost roller and the turnaround roller causes displacement of the roller relative to the turn around roller and the guide shoe. This causes the film to remain in contact with the guide shoe after it is threaded through the system possibly causing scratches of the film emulsion.
Allowance for such movement also increases the tolerance requirements of the system. Taking into account all of these required tolerances complicates the manufacturing process. Failure to take them into account contributes to less than optimum guide shoe performance and causes film artifacts.